This loop is from the book "50 Trail Runs in Southern California" by Stan Swartz, Jim Wolff and Samir Shahin, M.D.
Starting at the El Moro Visitor Center, take the El Moro Canyon Trail just below it. This description is clockwise (counter clockwise is fairly easy to figure out): At the top make a right at "Slow 'N Easy" and shortly after a right on Fence Line. Again a right on Moro Ridge Road. Look for the sign that says the road ends and go down on the right by taking Moro Ridge Spur. At the bottom take the single lane trail called B.F.I on the right, and you will be back to the start point.
The loop is mostly made of easy fire roads and 1.4 miles of single lane trail. Parking recommended in the book is at the El Moro Visitor Center, 8471 N Pacific Coast Hwy, Laguna Beach, CA 92651, but there is also a parking lot a bit further to the East, driving around the campground. At the time of this writing the parking cost $15 for the day and there are no free spaces close by.